Rotary blower



Jan- 15, 1946- R. P. MccuLLocH ET Al. 2,393,116

ROTARY BLOWER Filed March 20, 1942 4 Sheelcs-Sheet l EDbQZ-fEMEU//m Jan. l5, 1946. R p, MccuLLocH ETAL 2,393,l6

ROTARY BLOWER Filed March 20, 1942 l4 sheets-sheet 2 Jan. l5, 1946. R, P, MCCULLOCH ETAL 2,393,16

ROTARY BLOWER Filed March 20, 1942- 4 Sheets-Sheet 3 Jb Eyck:

Jan. l5, 1946. R, P, MccuLLocH ET AL 2,393,M6

ROTARY BLOWER Filed March 20, 1942 4 Sheets-Sheet 4 ENT/IPE AREA BOUNDED BY THIS LINE PHVIDED WITH CCNF'I GURATION INDICA TEU SMM E/Jbgr EMI/:UNDEh Jahn L .Fydp @dm Patented Jan. l5, 1946 ROTARY BLOWER Robert P. McCulloch and John L. Ryde, Milwaukee, Wis., assignors to B-W Superchargers, Inc., a corporation oi' Delaware Application March 20, 1942, Serial No. 435,566

Claims.

This invention relates torotary or positive displacement blowers or superchargers of the type used on Diesel engines to provide forced air induction and scavenging.

Such blowers comprise a pair of rotors having meshing lobes revolving in an appropriate housing or casing. The air or other iluid being pumped is trapped in the pockets between the lobes and the side walls of the casing and advanced from the inlet to the outlet, Consequently a pressure diierential obtains between the inlet and outlet.

This pressure differential tends to cause leaking of the parts was conducted with the greatest accuracy, production tolerances had to be maintained. In addition, expansion clearance had to be provided. This follows from the fact that while the rotors and castings may be made of .metal having the same coeilcients oi. expansion and contraction, a load suddenly applied on a cold blower would result in rapid expansion of the rotors well in advance oi any equivalent expansion on the part of the casing or housing.

Thus, unless adequate clearance existed between the ends of the rotors and the adjacent end walls of the casing or housing the rotors would bind and ruin the machine. Prior to this invention, nothing was done to reduce this clearance for as stated hereinbefore, its presence was regarded as an inherent and inevitable characteristic of this type of machine. The present invention, however, does contemplate the provision of means to reduce the leakage past the ends of the rotors to an inappreciable minimum.

To this end, it is an object of this invention to provide sealing means so designed and constructed that it may Ibe incorporated 'in blowers of this type without danger of having the rotors bind and without danger of pitting or scoring the surfaces of the end walls or the ends of the rotors.

Another object of this invention resides in the provision of novel sealing means carried by the rotor and so designed and constructed as to accommodate itself to the particular installation and automatically maintain a close but smoothrunning t between the ends of the rotors and the adjacent end walls.

Another object of this invention is to provide sealing means for the purpose described which may be quickly and easily replaced.

A further object of this invention is to provide sealing means for' the purpose described which is carried by the end Walls or plates of the housing and which presents a thin edge or multiplicity of edges to the ends of the rotors to automatically accommodate the seal to the installation without danger of scoring, pitting or otherwise injuring the rotors or any part of the blower.

With the above and other objects in view which will appear as the description proceeds, this invention resides in the novel construction, combination and arrangement of parts substantially as hereinafter described, and more particularly deiined by the appended claims, it being understood that such changes in the precise embodiment of the hereindisclosed invention may be made as come within the scope of the claims.

The accompanying drawings illustrate several complete examples of the physical embodiments of the invention constructed in accordance with the best modes so far devised for the practical application of the .principles thereof, and in which:

Figure 1 is an end view of a blower embodying this invention, parts thereof being broken away and in section;

Figure 2 is a, perspective view showing a portion of one end of one of the rotors with parts of the sealing means removed and separated to more clearly show their construction Figure 3 is a cross-sectional view through an end portion of the blower, said view being taken on the plane of the line 3-3 of Figure 1;

Figure 4 is a detail sectional view taken on the plane of the line 4-4 of Figure 1; e

Figure 5 is a perspective view of one end portion of a rotor illustrating the application of another form of sealing means thereto;

Figure 61s a view similar to Figure 3 but showing the application of the sealing means shown in Figure 5;

Figure 7 is a plan view of one of the end walls with the position of the rotors indicated thereon. and illustrating another embodiment of the invention;

Figure 8 is a detail sectional view taken through Figure 7 on the plane of the line 8 8;

Figure 9 is a plan view of one of the end walls equipped with another form of this invention;

and

` Figure 10 is an enlarged sectional view taken through part of Figure 9 on the plane of the line Ill-III.

Referring now particularly to the accompanying drawings, in which like numerals indicate like parts, the numeral 5 designates the casing or housing of a rotary 'or positive displacement type blower, the opposite side walls of which have an inlet S and an outlet 1 therein. The ends of the casing are closed -by flat end walls 8 bolted or otherwise secured thereto. These end walls carry bearings not shown in which the shafts 9 of rotors I0 rotate.

The rotors I are geared together by suitable gears (not sh'own) fixed to their shafts, and have meshing lobes il which sweep across the inner surfaces of the casing side walls and coact there with to form pockets l2 in which the air or other fluid being pumped is entrapped and carried from the inlet to the outlet. Obviously, therefore, during the operation of the blower a pressure differential obtains between the inlet and outlet.

This pressure differential causes leakage around the ends of the rotors, that is, between the ends of the rotors and the adjacent at inner surfaces of the end walls 8.

At the center. or between the axes of the rotors where the direction of motion of th'e rotor lobes corresponds to the direction of leakage, the extent of the leakage is greater than at the ends of the oval formed by the cross-sectional shape of the housing. Here the rotor lobes are travelling against the direction of leakage.

The skin friction between the ends of the lobes as they sweep around these outer arcs and the flat inner surfaces of the end walls with the consequent necessity for shearing the fluid b etween the ends of the rotors and the end walls at these pggttss, offsets to a great extent the leakage which e This indicates that a seal between the axes of the rotors would materially reduce the leakage and for this reason the construction shown in Figures I and 8 which is perhaps the most elementary of th'e four different forms of the invention shown, may be used to advantage.

In this embodiment of the invention, a sealing strip I3 is embedded in a groove Il in each end wall between the holes therein which accommodate the rotor shafts. The strips protrude from the smooth inner surfaces of the end walls and are secured in place preferably by swedging in the marginal edges of the groovesA as shown in detail in Figure 8.

Initially these strips project from the surfaces of the end walls a distance slightly in excess of the clearance between the rotor ends and the end walls, but being formed of material which will wear away smoothly and without danger of scoring or pitting the ends of the rotor, they are soon worn away to the proper height.` In actual practice, hard ber has been found practical for this embodiment of the invention, and the strip is about i! of an inch in thickness.

A more complete seal is effected by means of the construction shown in Figures 1 to 3, inclusive. In this case both ends of each rotor lobe are counterbored as at I to snugly receive sealing rings I6. Spider-like springs i1 yieldingly urge these rings outwardly of the counterbore into engagement with the adjacent flat surfaces of the end walls. The extremities of the arms of these springs engage under the rings while their medial portions bear against a diametrical rib Il cast into the rotor. 1

In addition, the ends of the rotor have three grooves i9 joining the three counterbores Il and snugly receiving strips or bars 20. The ends of The rings and bars are preferably formed of carbon so that they will wear smoothly and without danger of-scoring or pitting the surfaces of the end walls, and as will be readily apparent, as the rings and bars wear away, the springs behind them take up this wear and automatically hold the sealing members in position to take up aliciearance between the ends of the rotor and the casing end walls.

Another manner of providing the desired seal is illustrated in Figures 5 and 6. In this construction, an end plate 22 is secured to each end of each rotor. These end plates may be made in any suitable manner, but are preferably molded. 'I'hey have exactly the same contour as the rotors and are readily removably secured thereto by screws 23.

To properly locate-the end plates on the ends of the rotors, dowel projections 2l extend from the inner surface of the plates to engage in accurately machined sockets in the ends of the rotors.

Around the perimeter of each end plate is a thin ridge 25. An equivalent ridge or plurality of ridges 25' also encircles the hole 26 which accommodates the rotor shaft. These ridges are the only portions of the end plates which contact the inner surfaces of the end walls.

The end plates are formed of material which will wear away withoutdanger of scoring or pit-- ting the surfaces of the end walls. A phenolic condensation product has been found admirably suited for this purpose as this material chars rather than flows under the influence of heat so that the ridges can be worn away during expansion of the rotor without danger of scoring or pitting the surfaces of the end walls.

The embodiment of the invention shown in Figures 9 and l0 is a further development of the scheme shown in Figures '1 and 8. It consists of a multiplicity of tiny ridges 21 formed on the end walls 8 and covering the area thereof presented to thesweep of the rotors. These tiny ridges 21 are formed of rubber or synthetic rubber vulcanized or bonded as a thin sheet to the inner surfaces of the end walls, the ridges 21 being arranged in the manner of a gridiron and projecting a slight distance out from the surface of the sheet proper.

In actual practice the sheet of rubber or synthetic rubber has a thickness of approximately ten-thousandths (.010) of an inch and the ridges project upwardly therefrom twenty to twentyve-thousandths (.020 to .025) of an inch, and the edges of the ridges presented to the ends of the rotors are but one sixty-fourth (1m) of an inch wide. As will be readily apparent, this arrangement will produce an exceptionally effective seal without danger of injury to the rotors or any other portion of the machine.

From the foregoing description taken in connection with the accompanying drawings, it will be readily apparent to those skilled in the artthat this invention materially improves the efiiciency of rotary blowers by reducing the amount of leakage around the ends of the rotors to an inappreciable minimum and that the incorporation of the means employed to eect this result is practical and in nowise complicates the design of such blowers.

.What we claim as our invention is:

l. In a rotary blower of the character described: a rotor having spaced lengthwise extending lobes; a casing in which the'rotor rotates, said casing having an arcuate inner wall across which the lobes of the rotor sweep, and having flat end walls to which the ends of the rotor are adjacent, the lobes of the rotor having substantially circular recesses in each end; a sealing ring in each of said recesses; yieldable means projecting said sealing rings beyond the mouths of the recesses and into engagement with the at inner surfaces of the end walls; and sealing members extending between said sealing rings and likewise engaging the adjacent dat surfaces of the end walls.

2. In a rotary blower of the character described: a rotor having spaced lengthwise extending lobes; a casing in which the rotor rotates, said casing having an arcuate inner wall across which the lobes of the rotor sweep, and having ilat end walls to which the ends of the rotor are adjacent, said rotor having circular recesses in its lobes and grooves connecting the circular recesses; sealing rings in said circular recesses; sealing bars in said grooves; and springs in back of said sealing rings and sealing bars pressing the same outwardly against the at inner surfaces of the housingend walls to prevent iluid leakage around the ends of the rotor.

3. Sealing means for a fluid displacement device having a rotor with lobe-shaped blades that sweep an arcuate surface in a housing and the ends of the blades coact with end walls of the housing, comprising annular seats in the ends of the blade lobes conforming substantially with the cross-sectional contours of the lobes; form-retaining seal members in said seats engaged with the housing end walls; channels extending between and connecting said annular seats; and sealing bars in said channels for engagement with the housing end walls.

4. The improvements defined in cla/im 3 wherein the seal members and sealing bars are formed of material which will wear smoothly from contact with the housing end walls thereby to reduce fluid leakage around the rotor ends to an inappreciable minimum.

5. Sealing means for a fluid displacement de' vice having a rotor with lobe-shaped blades that sweep an arcuate surface in a housing and the ends of the blades coact with end walls of the housing, comprising annular seats in the ends of the blade lobes conforming substantially with the cross-sectional contours of the lobes; form-retaining seal members in said seats engaged with the housing end walls; channels extending between and connecting said annular seats in tangent relation to the rotor axis; and sealing bars in said channels for engagement with the housing end walls; and yieldable means urging said seal members and sealing bars into friction contact with the housing end walls.

ROBERT P. McCULLOCH. JOHN L. RYDE. 

